We're interested in Trello for game development. We're using Flowdock for our team inbox and chat, and would like all card changes in our Trello organization to trigger notifications in Flowdock. Flowdock can be integrated with other web apps via emails (sent to our team inbox), RSS, or an API. The easiest path would be email, but it appears that Trello only sends email notifications for a small subset of card changes (if you were personally added to a card, invited to something, etc.).

Is there a way to trigger Trello email for all card changes?
Otherwise, is the API the best way to integrate with an external app like Flowdock?